几道数学题求教~

timothyyung

GWD数学9-Q32
What is the remainder when the positive integer x is divided by 8?
(1)When x is divided by 12, the remainder is 5.
(2)When x is divided by 18, the remainder is 11.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


GWD数学10-Q4
If S is the sum of the reciprocals of the consecutive integers from 91 to 100, inclusive, which of the following is less than S?
Ⅰ1/8
Ⅱ 1/9
Ⅲ
1/10



A.None

B.I only
C.III only

D.II and III only

E.I, II, and III




GWD数学10-Q26

What is the greatest common factor of the positive integers j and k?
(1)k = j + 1
(2)jk is divisible by 5.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient

请牛人指点~十分感谢！！

If S is the sum of the reciprocals of the consecutive integers from 91 to 100, inclusive, which of the following is less than S?
Ⅰ1/8
Ⅱ 1/9
Ⅲ
1/10



A.None

B.I only
C.III only

D.II and III only

E.I, II, and III




GWD数学10-Q26

What is the greatest common factor of the positive integers j and k?
(1)k = j + 1
(2)jk is divisible by 5.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient

请牛人指点~十分感谢！！

michellehoS

If S is the sum of the reciprocals of the consecutive integers from 91 to 100, inclusive, which of the following is less than S?
这个是求1/91加到1/100吧，S应该是在1/91*10到1/100*10之间，就是10/91到1/10之间，所以S大于1/10，又因为10/90大于10/91，所以1/9比S大，1/8也比S大，答案应该C吧。。。。

rockstonexS

What is the greatest common factor of the positive integers j and k?
(1)k = j + 1
(2)jk is divisible by 5.
条件2单独显然不充分。
条件1中，k和j的值只相差1，所以最大公约数只可能是1啊，因为都是整数嘛，答案是A吗。。

timothyyung

S>10/91,1/9也大于10/91,那么S怎么就大于1/9了呢？

timothyyung

是A,谢谢~

citidandan

S>10/91,1/9也大于10/91,那么S怎么就大于1/9了呢？
timothyyung 发表于 2011-6-3 06:40

    S小于10/91，S的范围是大于10/100小于10/91

yayajiaojef

第一题是选C么。我采取的列举的方式，虽然比较笨，但时间不长~期待有人用更好的方法啊~！！

Fuckitup

第一题
我是带数值进去的，（1）里面x可以为17，也可以为 29. 这两个数 除以8 ，余数分别是1和5，所以（1）不行
（2）也一样，x为29或47 余数分别为 5 和7.
（1） 和（2）合并 我是假设x= 12a+5，y=18b+11
两者相等，得2a-3b=1，a和b都为整数，带几个数进去验证了一下，若b=1，a=2，则是x为29的情况，余数为5，而若b=3，a=5，这时x=65,余数为1
综上，这个题应该选E。。。。。不知道对不对
好麻烦，我自己都要吐了，但是我数学分析能力很差，一般都直接带数进去算的。